This invention relates to a communication device applied in a code division multiple access (CDMA) communication system and a method thereof. More particularly this invention relates to a spread spectrum communication device for improving interleave transmission and transmission power control in spread spectrum communication, and for realizing handovers between different frequencies and a method thereof.
In a CDMA cellular system, because the same carrier frequency is used repeatedly in every cell there is no need for handovers between frequencies within the same system. However, considering a case such as when existing systems are present together, there is a need for handovers between different carrier frequencies. Three points pertaining to detailed cases are described below.
As a first point, in a cell where there is considerable traffic, a separate carrier frequency is used to accommodate the increased number of subscribers, and a handover may be performed between those cells. As a second point, when an umbrella cell constitution is used, different frequencies are allocated to large and small cells, and handovers are performed between the cells. Then, as a third point, there are cases of handovers between a third generation system, such as a W(Wideband)-CDMA system, and a second generation system, such as a current mobile telephone system.
When performing handovers in cases such as those mentioned above, it is necessary to detect the power of carriers at the different frequencies. To achieve this detection, the receiver needs to only have a structure capable of detecting two frequencies. However, this increases the size of the constitution of the receiver, or makes the constitution complicated.
Furthermore, two types of handover method may be considered: a mobile assisted handover (MAHO) and a network assisted handover (NAHO). Comparing the MAHO and NAHO methods, NAHO reduces the burden of the mobile device, but to be successful, it should be necessary to synchronize the mobile device and the base station, whereby the constitution of the base station and the network becomes complicated and large in order to be capable of tracking each individual mobile device.
For such reasons, the realization of the MAHO method is more desirable, but to determine whether or not to handover, it is necessary to measure the strength of carriers of different frequencies at the mobile devices. However, a CDMA cellular system differs from a time division multiplex access (TDMA) system used in a second generation, in that it uses ordinarily continuous transmission for both transmission/reception. In this continuous transmission/reception technique, unless receivers corresponding to two frequencies are prepared, it is necessary to stop the timing of the transmission or the reception and measure the other frequency.
There has been disclosed a technique relating to a compressed mode method, for time-compressing the transmission data in the usual mode and transmitting it in a short time, thereby creating some spare time which can be utilized to measure the other frequency carrier . As an example of this, there is Japan Patent Application National Publication (Laid-Open) (JP-A) No. 8-500475 xe2x80x9cNon-continuous Transmission for Seamless Handovers in DS-CDMA Systemsxe2x80x9d. This application discloses a method of realizing a compressed mode, wherein the spreading factor of the spreading code used is lowered to compress the transmission duration.
The method of realizing the compressed mode according to the above application will be explained below. FIG. 36 shows an example of transmissions in a normal mode and a compressed mode in a conventional CDMA system. In FIG. 36, the vertical axis represents transmission rate/transmission power, and the horizontal axis represents time. In the example of FIG. 36, the compressed mode transmission is inserted between normal transmission frames.
In the transmission in the compressed mode, a non-transmission timing is provided in the downlink frame, and can be set to a desired period of time (duration). This non-transmission timing represents idle period during which the strength of the other frequency carrier is measured. In this way, slotted transmission can be achieved by inserting the idle period during transmission of compressed mode frames.
In this type of compressed mode transmission, transmission power increases in accordance with the time ratio between the idle period and the frame (compressed mode frame) transmission timing, and therefore, as shown in FIG. 36, the compressed mode frame is transmitted at a higher transmission power than the frame in normal transmission. As a consequence, transmission quality can be maintained even in frame transmission in compressed mode.
In addition to the application mentioned above, as an example of pertinent literature there is Gustafsson, M. et al: xe2x80x9cCompressed Mode Techniques for Inter-Frequency Measurements in a Wide-band DS-CDMA Systemxe2x80x9d, Proc. of 8th IEEE PIMRC ""97. This research paper discloses techniques for realizing compressed mode in cases other than when the spreading factor is lowered, namely when the coding rate is increased, when multi-code transmission is used, and when a multi-bit transmission modulation system such as 16QAM is used.
However, in conventional examples such as the application mentioned above, since transmissions are interleaved in units of one frame and within one frame, the interleaving time for slotted transmission (in the compressed mode) is more compressed than in normal transmission. Consequently, the interleaving size is shortened which leads to a problem of poor decoding at the reception side.
Furthermore, in conventional examples such as the literature mentioned above, since the length of interleaving time is shortened when using compressed mode transmission, there is increased deterioration of signal quality with respect to fading, and, since no TPC (transmission power control) command bit is sent during non-transmission, it is not possible to achieve high-speed TPC, leaving a subsequent problem of poor signal quality.
Furthermore, in conventional examples such as the application and literature mentioned above, the spreading factor is lowered when carrying out a compressed mode transmission. However, in general, lowering of the spreading factor indicates that a spreading code having a short code-length is being used. However, since the number of spreading codes that can be used is directly proportional to the square of the code-length, there is a problem that there are extremely few spreading codes having short code-lengths, and these spreading code resources, which are vital for realizing compressed mode transmission, are consumed.
It is an object of the present invention to solve the problems described above by providing a spread spectrum communication device and a spread spectrum communication method capable of preventing deterioration in signal quality caused by compressed mode, with respect to interleaving, transmission power control, spreading code allocation methods and the like to minimize the effects of transmission errors.
A spread spectrum communication device according to an aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises an interleaving unit for interleaving in bit units a frame or a compressed frame, which is a unit of a transmission data stream, to minimize effects of transmission errors; a compressing/intermittent transmitting unit for compressing a frame prior to or after interleaving in the compressed mode, and moreover, intermittently outputting the compressed frame to the interleaving unit if the compressed frame has not yet been interleaved, and intermittently outputting the compressed frame to a device on a reception side if the compressed frame has been interleaved; a control unit for controlling the operation of interleaving in bit units of the interleaving unit, and the compressing/intermittent transmitting operation of the compressing/intermittent transmitting unit; the control unit controlling the interleaving unit to perform interleaving in bit units across multiple frames in the compressed mode.
According to this invention, in the compressed mode, multiple frames are interleaved in bit units to minimize effects of transmission errors, whereby it is possible to secure appropriate interleaving time in the compressed mode in the same way as in the normal mode, and consequently, poor performance caused by interleaving in bit units can be prevented.
A spread spectrum communication device according to a next aspect of the invention is characterized in that the interleaving unit has a memory size in correspondence with the number of frames to be interleaved in the compressed mode.
According to this invention, since the memory size used is in correspondence with the number of frames to be interleaved in the compressed mode, interleaving in bit units can be performed in a number of frames sufficient to minimize the effects of transmission errors in the compressed mode.
A spread spectrum communication device according to a next aspect of the invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and characterized in that it comprises an interleaving unit for interleaving in bit units a frame or a compressed frame, which is a unit of a transmission data stream, to minimize effects of transmission errors; a compressing/intermittent transmitting unit for compressing a frame prior to or after interleaving in the compressed mode, and moreover, intermittently outputting the compressed frame to the interleaving unit if the compressed frame has not yet been interleaved, and intermittently outputting the compressed frame to a device on a reception side if the compressed frame has been interleaved; a control unit for controlling the interleaving operation in bit units of the interleaving unit, and the compressing/intermittent transmitting operation of the compressing/intermittent transmitting unit; the control unit controlling the compressing/intermittent transmitting unit so that the compressed frame is divided to the front and rear of the same frame timing as in the normal mode.
According to this invention, in the compressed mode, the compressed frame is divided to the front and rear of the same frame timing as in the normal mode, and intermittently transmitted in that arrangement, and consequently, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode using a simple interleaving constitution so that the effects of transmission errors caused by interleaving in bit units can be further reduced.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the control unit controls the interleaving unit so that, in the compressed mode, interleaving in bit units is performed across multiple frames.
According to this invention, in the compressed mode, since interleaving is controlled so that interleaving in bit units is performed across multiple frames, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, and consequently, the effects of transmission errors caused by interleaving in bit units can be further reduced.
A spread spectrum communication device according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting multiple frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a compressing/intermittent transmitting unit for compressing a frame, which comprises multiple slots and is a unit of a transmission data stream, and intermittently transmitting the compressed frame; and a control unit for controlling the compressing/intermittent transmitting unit so as to slot the compressed frame, and intermittently transmit the slotted frame in N (a natural number) slot units.
According to this invention, in the compressed mode, the compressed frame is slotted, and intermittently transmitted in N slot units, and therefore, transmission power control bits transmitted in a downlink can be received in comparatively short time intervals, whereby the amount of transmission power control error can be reduced.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the control unit determines the N slot units in accordance with the relationship between the measuring time of another frequency carrier component and the amount of transmission power control error.
According to this invention, since the N slot units are determined in accordance with the relationship between the measuring time of another frequency carrier strength and the amount of transmission power control error, it is possible to secure time for reliably measuring the strength of other frequency carriers, and in addition, the amount of transmission power control error can be greatly reduced.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that it further has an interleaving unit for interleaving in bit units a frame or a compressed frame, which is a unit of a transmission data stream, to minimize effects of transmission errors; the control unit controlling the interleaving unit so that, in the compressed mode, interleaving in bit units is performed across multiple frames.
According to this invention, in the compressed mode, since interleaving in bit units is controlled across multiple frames, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, and consequently, the effects of transmission errors caused by interleaving in bit units can be further reduced.
A spread spectrum communication device according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises an interleaving unit for interleaving in bit units a frame or a compressed frame, which is a unit of a transmission data stream, to minimize effects of transmission errors; a compressing/intermittent transmitting unit for compressing a frame prior to or after interleaving in the compressed mode, and moreover, intermittently outputting the compressed frame to the interleaving unit if the compressed frame has not yet been interleaved, and intermittently outputting the compressed frame to a device on a reception side if the compressed frame has been interleaved; a control unit for controlling the interleaving in bit units operation of the interleaving unit, and the compressing/intermittent transmitting operation of the compressing/intermittent transmitting unit; wherein in the compressed mode, the control unit controls the compressing/intermittent transmitting unit so that multiple frames prior to interleaving in bit units by the interleaving unit, or multiple frames after interleaving, are compressed using code-multiplexing in a given frame timing.
According to this invention, in the compressed mode, multiple interleaved frames are compressed using code-multiplexing in a given frame timing and intermittently transmitted, whereby an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, and consequently, performance deterioration caused by interleaving in bit units can be prevented.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the control unit controls the interleaving unit so that, in the compressed mode, interleaving is performed in bit units across multiple frames.
According to this invention, in the compressed mode, interleaving is performed in bit units across multiple frames, and therefore, a longer interleaving duration can be secured in the compressed mode than in the normal mode, whereby the effects of transmission errors caused by interleaving in bit units can be further reduced. In particular, if other frames are replaced by multi-code-transmitted frames and interleaving is performed, it is possible to disperse multiple multi-code-transmitted frames which are in error in the same place, thereby increasing the correcting capability of the error-correction encoding.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the compressing/intermittent transmitting unit has a memory size in correspondence with the number of frames to be code-multiplexed in the compressed mode.
According to this invention, since the memory size used is in correspondence with the number of frames to be code-multiplexed in the compressed mode, code-multiplexing can be realized reliably and without loss in the compressed mode.
A spread spectrum communication device according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, is characterized in that it comprises a compressing/intermittent transmitting unit for compressing a frame, which is a unit of a transmission data stream, and intermittently transmitting the compressed frame, in the compressed mode; and a control unit for controlling the compressing/intermittent transmitting unit so that, in the compressed mode, the compressing/intermittent transmitting unit intermittently transmits at a lower transmission rate than the transmission rate in the normal mode, while using the same transmission power as in the normal mode.
According to this invention, in the compressed mode, the compressing/intermittent transmitting unit intermittently transmits at a lower transmission rate than the transmission rate in the normal mode, while using the same transmission power as in the normal mode, and consequently, the there is less interference power on other users on the same frequency during a frequency handover, enabling the frequency handover to be realized with reduced interference.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that it further comprises an interleaving unit for interleaving in bit units a frame or a compressed frame, which is a unit of a transmission data stream, to minimize effects of transmission errors; the control unit controlling the interleaving- unit so that, in the compressed mode, interleaving in bit units is performed across multiple frames.
According to this invention, in the compressed mode, interleaving in bit units is performed across multiple frames, and therefore an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, and consequently, the effects of transmission errors caused by interleaving in bit units can be further reduced.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the control unit controls the compressing/intermittent transmitting unit so that the compressed frame is divided to the front and rear of the same frame timing as in the normal mode.
According to this invention, since the compressed frame is divided to the front and rear of the same frame timing as in the normal mode, and intermittently transmitted in compliance with that arrangement, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode with a simple interleave constitution, and consequently, deterioration in performance caused by interleaving in bit units can be further reduced.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the control unit controls the compressing/intermittent transmitting unit so as to slot the compressed frame, and intermittently transmit the slotted frame in N (a natural number) slot units.
According to this invention, in the compressed mode, the compressed frame is slotted and intermittently transmitted in N slot units; therefore, transmission power control bits transmitted in a downlink can be received in comparatively short time intervals, whereby the amount of transmission power control error can be reduced.
A spread spectrum communication device according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a memory unit for storing optimum transmission power control units for the normal mode and the compressed mode, so that the transmission power control unit controlling one output of transmission power is greater in the compressed mode than in the normal mode; and a transmission power control unit for referring to the memory unit, and controlling transmission power to a communication partner device in compliance with transmission power control units in correspondence with the normal mode and the compressed mode, based on information representing a reception power received from the communication partner device.
According to this invention, in the compressed mode, transmission power to the communication partner device is controlled so that a transmission power control unit for one time is greater in the compressed mode than in the normal mode, and consequently, in the compressed mode, even when the temporal intervals of the transmission power control during intermittent transmission are wider, it is possible to widen the control range of the transmission power and maintain adhesion to the transmission power in the compressed mode, whereby the amount of error of transmission power control in the compressed mode can be reduced.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that it further comprises a compressing/intermittent transmitting unit for compressing a frame, which comprises multiple slots and is a unit of a transmission data stream, and intermittently transmitting the compressed frame; and a control unit for controlling the compressing/intermittent transmitting unit so as to slot the compressed frame, and intermittently transmit the slotted frame in N (a natural number) slot units.
According to this invention, in the compressed mode, the compressed frame is slotted, and intermittently transmitted in N slot units, and therefore, transmission power control bits transmitted in a downlink can be received in comparatively short time intervals, whereby the amount of transmission power control error can be reduced.
A spread spectrum communication device according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a memory unit for taking more multiple types of transmission power control unit than in the normal mode, a transmission power control controlling one input of transmission power, including among the multiple types of transmission power control unit a transmission power control unit which is greater than in the normal mode, and storing optimum transmission power control units for the normal mode and the compressed mode; a transmission power control unit for referring to the memory unit, and controlling transmission power to a communication partner device in compliance with transmission power control units in correspondence with the normal mode and the compressed mode, and in addition, in correspondence with temporal intervals in the transmission power control in the compressed mode, based on information representing a reception power received from a communication partner device.
According to this invention, transmission power to a communication partner device is controlled in compliance with transmission power control units in correspondence with the normal mode and the compressed mode, and in addition, in correspondence with temporal intervals in the transmission power control in the compressed mode; therefore, even when the temporal intervals of the transmission power control during intermittent transmission alter, by utilizing the control range of the transmission power it is possible to maintain adhesion to the transmission power in the compressed mode, thereby reducing the amount of error of transmission power control in the compressed mode.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that it further comprises a compressing/intermittent transmitting unit for compressing a frame, which comprises multiple slots and is a unit of a transmission data stream, and intermittently transmitting the compressed frame; and a control unit for controlling the compressing/intermittent transmitting unit so as to slot the compressed frame, and intermittently transmit the slotted frame in N (a natural number) slot units.
According to this invention, in the compressed mode, the compressed frame is slotted, and intermittently transmitted in N slot units, and therefore, transmission power control bits transmitted in a downlink can be received in comparatively short time intervals, whereby the amount of transmission power control error can be greatly reduced.
A spread spectrum communication device according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a transmission section for using a desired spreading code to create transmission data of a quantity corresponding to a number of users who can be served thereby, in correspondence with the normal mode and the compressed mode, and adding and transmitting the transmission data created in correspondence with the number of users; and a compressed mode control section, connected to the transmission section, for controlling the creation operation of transmission data by the transmission section in the compressed mode; the compressed mode control section having a frame combining unit for extracting from given combinations of multiple compressed mode frames, compressed by separate users in the transmission section, a combination having a total transmission duration of less than one frame duration; a spreading code allocation unit for allocating the same spreading code to each of multiple channels which transmit the combination extracted by the frame combining unit; and a transmission timing control unit for using a single spreading code, allocated by the spreading code allocating unit, to control the transmission section so that transmission timings of multiple compressed mode frames, which comprise the above extracted combination, do not temporally overlap within one frame duration.
According to this invention, the compressed mode control section extracts from given combinations of multiple compressed mode frames, compressed by separate users in the transmission section, a combination having a total transmission duration of less than one frame duration, allocates the same spreading code to each of multiple channels which transmit the combination extracted by the frame combining unit, and uses a single spreading code, allocated by the spreading code allocation unit, to control the transmission section so that transmission duration of multiple compressed mode frames, which comprise the above extracted combination, do not temporally overlap within one frame duration; therefore, when there are multiple compressed mode frames, the number of spreading codes with low spreading factor used in the compressed mode can be reduced, and consequently, the spreading code resources can be effectively used in the compressed mode.
A spread spectrum communication device according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a compressing/intermittent receiving unit for intermittently receiving a compressed frame in the compressed mode; search code detecting and determining unit for detecting on other frequency carriers, during non-transmission period in the compressed mode, a first search code, which is shared at all base stations and is time-continually transmitted, and a second search code, which is transmitted at the same timing as the first search code and can be identified by multiple numeric patterns, and determining these search codes based on a predetermined reference; a control unit for selecting the compressing/intermittent receiving unit during intermittent receiving, selecting the search code detecting and determining unit during non-transmission duration, and controlling operations of both; the control unit establishing synchronization to the other frequency carrier, based on the first search code and second search code detected by the search code detecting and determining unit, and thereby controlling a handover between different frequencies.
According to this invention, synchronization to another frequency carrier is established based on the first search code and second search code detected by the search code detecting and determining unit, thereby enabling a handover to be efficiently performed between different W-CDMA/W-CDMA frequencies.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the control unit carries out control to detect at least one first search code during the non-transmission period which is not more than half of one frame, and thereafter, carries out control to repeat the processing of shifting the non-transmission period by a predetermined slot unit, and to detect a numeric value of all second search codes using multiple frames, and to establish synchronization to the other frequency carrier, based on the detected first search code and the numeric pattern of second search code, thereby controlling a handover between different frequencies.
According to this invention, at least one first search code is detected during the non-transmission period which is not more than half of one frame, and thereafter, the processing of shifting the non-transmission period by a predetermined slot unit is repeated, a numeric value of all the second search codes is detected using multiple frames, and synchronization is established to the other frequency carrier based on the detected first search code and the numeric pattern of second search code, thereby enabling a handover to be even more efficiently performed between different W-CDMA/W-CDMA frequencies.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the non-transmission duration can be arranged across multiple frames.
According to this invention, since the non-transmission period can be arranged across multiple frames, the second search codes can be detected multiple times, improving the reliability of the detected codes.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that, when no search code can be obtained which satisfies a predetermined level of reliability during the search code detection, a search code is detected again in the place.
According to this invention, when no search code can be obtained which satisfies a predetermined level of reliability during the search code detection, a search code is detected again in the place, and consequently, synchronization can be established based on information of high reliability.
A spread spectrum communication device according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a compressing/intermittent receiving unit for intermittently receiving a compressed frame in the compressed mode; information detecting and determining unit for detecting in another communication system, during non-transmission period in the compressed mode, a first information for matching frequencies, and a second information for achieving synchronization, and determining the first and second information based on a predetermined reference; a control unit for selecting the compressing/intermittent receiving unit during intermittent receiving, selecting the information detecting and determining unit during non-transmission period, and controlling operations of both; the control unit establishing synchronization to the other communication system, based on the first information and second information detected by the information detecting and determining unit, and thereby controlling a handover between different frequencies.
According to this invention, synchronization to another communication system is established based on the first information and second information detected by the information detecting and determining unit, thereby enabling a handover between different frequencies to be achieved efficiently.
A spread spectrum communication device according to a next aspect of the present invention is characterized in that the control unit carries out control to detect at least one first information during the non-transmission period which is not more than half of one frame, thereafter, carries out control to set the non-transmission period based on a time found by the detected first information, and to detect the second information, and establishes synchronization to the other communication system, based on the detected first information and second information, thereby controlling a handover between different frequencies.
According to this invention, at least one first information is detected during the non-transmission period which is not more than half of one frame, thereafter, the non-transmission period is set based on a time found by the detected first information, the second information is detected, and synchronization to the other communication system is established based on the detected first information and second information; therefore, a handover between different systems can be carried out more effectively.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of interleaving of interleaving bit units across multiple frames, in order to minimize effects of transmission errors, in the compressed mode; a second step of compressing a frame interleaved in bit units in the first step, and intermittently transmitting it.
According to this invention, in the compressed mode, in order to minimize effects of transmission errors, interleaving of bit units is performed across multiple frames, and the interleaved frame is compressed and intermittently transmitted; therefore, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, and consequently, deterioration in performance caused by interleaving in bit units can be prevented.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of compressing a frame, which is a unit of a transmission data stream, and intermittently outputting it, in the compressed mode; and a second step of interleaving bit units across a plurality of the compressed frames.
According to this invention, in the compressed mode, a frame, which is a unit of a transmission data stream, is compressed and output intermittently, and interleaving in bit units is performed across multiple compressed frames; consequently, therefore, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, and deterioration in performance caused by interleaving in bit units can be prevented.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of interleaving bit units of a frame, which is a unit of a transmission data stream, and intermittently outputting it, in order to minimize effects of transmission errors; and a second step, performed in the compressed mode, of compressing a frame interleaved in bit units in the first step, dividing the compressed frame to the front and rear of the same frame timing as in the normal mode, and intermittently transmitting it.
According to this invention, in the compressed mode, a frame interleaved in bit units is compressed, divided to the front and rear of the same frame timing as in the normal mode, and intermittently transmitted; consequently, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, whereby performance deterioration caused by interleaving in bit units can be prevented.
A spread spectrum communication method according to the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step, performed in the compressed mode, of compressing a frame, which is a unit of a transmission data stream, and interleaving bit units of the compressed frame; and a second step of dividing the compressed and interleaved frame to the front and rear of the same frame timing as in the normal mode, and intermittently transmitting it.
According to this invention, in the compressed mode, a frame, which is a unit of a transmission data stream, is compressed and interleaved in bit units, divided to the front and rear of the same frame timing as in the normal mode, and intermittently transmitted; consequently, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, whereby performance deterioration caused by interleaving in bit units can be prevented.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of dividing a frame, being a unit of a transmission data stream, into multiple slots in the compressed mode; and a second step of intermittently transmitting the frame slotted in the first step in N (N=a natural number) slot units.
According to this invention, in the compressed mode, the compressed frame is slotted, and intermittently transmitted in N slot units, and therefore, transmission power control bits transmitted in a downlink can be received in comparatively short time intervals, whereby the amount of transmission power control error can be greatly reduced.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of interleaving in bit units a frame, being a unit of a transmission data stream, in order to minimize effects of transmission errors; a second step, performed in the compressed mode, of using code-multiplexing to compress, in a given frame timing, multiple frames interleaved in bit units in the first step, and transmit them intermittently.
According to this invention, in the compressed mode, code-multiplexing is used to compress, in a given frame timing, multiple frames interleaved in bit units, and they are transmitted intermittently; consequently, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, whereby performance deterioration caused by interleaving in bit units can be prevented.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step, performed in the compressed mode, of using code-multiplexing to compress, in a given frame timing, multiple frames interleaved in bit units in the first step, and transmit them intermittently; and a second step of interleaving the compressed frames in bit units.
According to this invention, in the compressed mode, code-multiplexing is used to compress, in a given frame timing, multiple frames interleaved in bit units, and they are transmitted intermittently; consequently, an appropriate interleaving duration can be secured in the compressed mode as in the normal mode, whereby performance deterioration caused by interleaving in bit units can be prevented.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of compressing a frame, which is a unit of a transmission data stream, in the compressed mode; and a second step of using the same transmission power as in the normal mode to transmit the frame compressed in the first step at a lower transmission rate than in the normal mode.
According to this invention, in the compressed mode, the same transmission power as in the normal mode is used to intermittently transmit a compressed frame at a lower transmission rate than in the normal mode; therefore, during a handover between frequencies, the amount of interference power to other users on the same frequency is reduced, whereby a handover between frequencies with reduced interference can be achieved.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of receiving information representing received power from a communication partner device; a second step of preparing beforehand a table storing optimum transmission power control units for the normal mode and the compressed mode, so that the transmission power control unit controlling one input of transmission power is greater in the compressed mode than in the normal mode, referring to the table, and determining transmission power for the normal mode and the compressed mode, based on the information representing received power received in the first step; and a third step of transmitting to the communication partner device in compliance with the transmission power determined in the second step.
According to this invention, by referring to a table storing optimum transmission power control units for the normal mode and the compressed mode, so that the transmission power control unit controlling one input of transmission power is greater in the compressed mode than in the normal mode, based on the information representing received power received from a communication partner device, transmission powers for the normal mode and the compressed mode are determined, and in the compressed mode, transmission is carried out so that the transmission power control unit controlling one input of transmission power is greater in the compressed mode than in the normal mode; therefore, in the compressed mode, even when the temporal intervals of the transmission power control during intermittent transmission are wider, it is possible to widen the control range of the transmission power and maintain adhesion to the transmission power in the compressed mode, whereby the amount of error of transmission power control in the compressed mode can be reduced.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of receiving information representing received power from a communication partner device; a second step of taking more multiple types of transmission power control unit than in the normal mode, a transmission power control controlling one input of transmission power, including among the multiple types of transmission power control unit a transmission power control unit which is greater than in the normal mode, preparing beforehand a table storing optimum transmission power control units for the normal mode and the compressed mode, referring to the memory unit, and determining transmission power in correspondence with the normal mode and the compressed mode, and in addition, in correspondence with temporal intervals in the transmission power control in the compressed mode, based on information representing a received power received in the first step; and a third step of transmitting to the communication partner device in compliance with the transmission power determined in the second step.
According to this invention, with regard to a transmission power control unit controlling one input of transmission power, more multiple types of these transmission power control units are taken than in the normal mode, including among the multiple types of transmission power control unit a transmission power control unit which is greater than in the normal mode, a table storing optimum transmission power control units for the normal mode and the compressed mode is referred to, and transmission power is determined in correspondence with the normal mode and the compressed mode and in addition, in correspondence with temporal intervals in the transmission power control in the compressed mode, based on information representing a reception power received from the communication partner device; and transmission is carried out in compliance with the determined transmission powers; therefore, in the compressed mode, even when the temporal intervals of the transmission power control during intermittent transmission alter, by utilizing the control range of the most suitable transmission power it is possible to maintain adhesion to the transmission power, thereby reducing the amount of error of transmission power control in the compressed mode.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first step of compressing frames, being units of a transmission data stream, in multiple transmission channels performing compressed mode transmission; a second step of extracting from given combinations of multiple compressed mode frames, compressed separately for users in the first step, a combination having a total transmission duration of less than one frame duration; a third step of allocating the same spreading code to each of multiple channels which transmit the combination extracted in the second step; and a fourth step of using the same spreading code, allocated in the third step, to transmit multiple compressed mode frames, which comprise the combination extracted in the second step, so that their transmission duration do not temporally overlap within one frame duration.
According to this invention, in multiple transmission channels where compressed mode transmission is being performed, frames which are units of a transmission data stream are compressed; a combination having a total transmission duration of less than one frame duration is extracted from given combinations of multiple compressed mode frames, compressed separately for users; the same spreading code is allocated to each of multiple channels which transmit the extracted combination; and the same spreading code is used to transmit multiple compressed mode frames, comprising the extracted combination, so that their transmission duration do not temporally overlap within one frame duration; therefore, the number of spreading codes with low spreading factor used in the compressed mode can be reduced, and consequently, the spreading code resources can be effectively used in the compressed mode.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first search code detecting step of detecting at least one first search code during the non-transmission period which is not more than half of one frame; a second search code detecting step of thereafter repeating the processing of shifting the non-transmission period by a predetermined slot unit, and detecting a numeric value of all second search codes using multiple frames; a handover between different frequencies being controlled by establishing synchronization to another frequency carrier, based on the detected first search code and the numeric pattern of second search code.
According to this invention, at least one first search code is detected during the non-transmission period which is not more than half of one frame, thereafter, the process of shifting the non-transmission timing by a predetermined slot unit is repeated, a numeric value of all second search codes is detected using multiple frames, and based on the detected first search code and the numeric pattern of second search code, synchronization is established to another frequency carrier; consequently, a handover between different W-CDMA/W-CDMA frequencies can be effectively performed.
A spread spectrum communication method according to a next aspect of the present invention is characterized in that the non-transmission period can be arranged across multiple frames.
According to this invention, since the non-transmission period can be arranged across multiple frames, the second search codes can be detected multiple times, improving the reliability of the detected codes.
A spread spectrum communication method according to a next aspect of the present invention is characterized in that, when no search code can be obtained which satisfies a predetermined level of reliability during the search code detection, a search code is detected again in the place.
According to this invention, when no search code can be obtained which satisfies a predetermined level of reliability during the search code detection, a search code is detected again in the place, enabling synchronization to be established based on information of high reliability.
A spread spectrum communication method according to a next aspect of the present invention is applied in a code division multiple access system for continuously transmitting frames in a normal mode, and intermittently transmitting compressed frames in a compressed mode, and is characterized in that it comprises a first information detecting step of detecting a first information for matching frequencies during non-transmission period which is not more than half of one frame; a second information detecting step of detecting second information for setting the non-transmission duration, based on a known timing determined beforehand from the detected first information, and achieving synchronization; a handover between different frequencies being controlled by establishing synchronization to another communication system, based on the detected first information and second information.
According to this invention, at least one first information is detected during the non-transmission period which is not more than half of one frame, thereafter, the non-transmission period is set based on a known timing found by the detected first information, the second information is detected, and synchronization to the other communication system is established based on the detected first information and second information; therefore, a handover between different systems can be carried out more effectively.